1. Field of the Invention
This invention relates to laminated rigid boards which have outer sheets adhered to a plastic foam core. These boards find use as heat insulating panels in construction. They have very high insulation value compared to other types of insulation and because of their light weight are easily handled and applied. The present invention will be described in the environment of making a roof insulation sheet, although the teachings of the invention should not be so limited.
2. Description of the Prior Art
The prior art process for making such boards is a continuous process in which a liquid of formable plastic is deposited between two sheets and is allowed to expand against parallel spaced platens on upper and lower conveyors. Since the foam core expands in all directions, it has been the practice to have the enclosing sheets be substantially wider than the desired width of the final product. The foam core hardens and ridigifies as a chemical reaction continues. As the rigid board is removed from the outlet end of the conveyor, trim saws cut the excess material along the longitudinal edges of the board to produce a board of predetermined width. The excess trim material presents a disposal problem, as well as an added cost in raw materials which must be discarded.
For example, it has been customary in producing a board of 48 inch width to have the foam extend as much as 5 inches or more on each side of the machine. The resulting losses in trim material are substantial.